Images for outside display, e.g., graphic displays on vehicle sides etc. should exhibit durability and weatherability. There is currently a need for a method of producing such images that is cheap and simple, and suitable for single image or low volume production.
The advent of electrophotographic copying, commonly referred to as xerography or plain paper copying, has proved to be a highly successful process for reproduction of images on to paper with the inherent advantages of speed and reliability. In a conventional process, an electrostatic image of an object is formed on a recording member such as a plate or drum. The recording member may comprise a layer of photoconductive material, such as selenium, on a conductive metal layer. The latent electrostatic image which is formed on the photoconductive material is developed into a visible image by application of toner powder or liquid and the image is transferred to a sheet of paper and affixed thereon by fusing, e.g., by application of heat and pressure, to form a permanent print. Full colour images may be obtained by sequentially forming electrostatic colour separation images on the recording member and using magenta, cyan, yellow and black toners in turn.
More recent developments in plain paper copiers include the ability to electronically store an image and output the image in sections at a predetermined level of magnification. Thus, a relatively large image may be output as a series of A4 or A3 sized sections ("tiles"), each of which bears a portion of the final image. When the tiles are placed in edge-to-edge abutment (after trimming any overlaps), the complete image is displayed.
U.S. Pat. No. 4,657,831 describes an electrostatic proofing method whereby a full-colour toner image is deposited on a thermoplastic layer applied to a photoconductive member, then transferred along with the thermoplastic layer to an opaque substrate and finally over-laminated with a transparent layer. Examples are known of a toner image being formed on a photoconductive member and transferred to a transfer sheet (rather than plain paper), whence it is subsequently transferred by heat and/or pressure to another substrate. This method is frequently used to produce lettering or graphics on tee-shirts, etc. (as described in GB1,568,226 and GB1,570,20l), or to produce dry-transfer materials for the graphic artwork industry (as described in EP094, 845 and GB2,079,219). None of these prior art methods addresses the problem of producing high-quality signs for outdoor use, and none of them is suitable for producing magnified images via the assembly of component "tiles".
The present invention utilises a plain paper copier to produce a toner image either as a single image or as a series of component tiles, which is transferred to a substrate and overlaminated to provide a durable image.